Fractionating method



Maly 23, 1933. o- BEHlMER 1,910,587

muy@

Patented May 23, 1933 entre STATES PATENT oFFlcE OTTO BEHIMER, CHICAGO, ILLINOIS, ASSIGNOR TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A. CORPORATION OF DEL-AW'AR-E y rnAcrIoNA'rINe METHOD handling of vapor sl of oil which have been generated in a still or the like and more 5 particularly it has rreference to the separation or fractionati pressure.

on of such vapors under In the distillation or cracking of oils, fractionating columns For the purpose of diverting the vapors in their passage through the tower, the latter may be filled with rock or other suitable material, orL it may be provided with a series of bubble trays which carry layers of oil through which the In one common vapors are forced to pass. form of tower, the trays are provided with tubular openings which are covered by suitable-caps that serve to divert the vapors and Jforce them downwardly through the layers of oil within the trays.

A portion of the vapors will be condensed in passing through the tower but if no means were provided to aid in cooling the latter,

its temperature would soon be raised to such a point that heavy,

undesirable constituents would be carried through and into the final condenser. In order to maintain the proper temperature within the tower, cooler oil ,is

r usually introduced at the top and allowed to gravitate toward the bottom` through suitable vent'pipes arranged ata desired flow level within each of the trays.

over- This cooler oil has in the past been supplied' largely from refiuX condensers which have been placed in theV vapor line leadingfrom the tower and which have been cooled by air or any other lsuitable means to, causea return of a portion of the vapors in the form of refiux condensate. It has also been proposed in the past to pump gasoline or vother light constituents of oil from storage into the top of the tower to supply the desired cooling efith the present invention it is contemplated topump'the gasoline or other final condensate into the top of the tower but in lieu of taking this refluXing material from storage, it is it from some point in the the pressure 1s substantially proposed to take system at which the same as that maintained on thetower itself. This pointmay either be at some intermediate location in the coil of the filial condenser or it may be beyond the latter but in ladvancevoi? the point at which the pressure is released by the control valves on an accumulator drum connected with the condenser.

withing the latter.

All that is required is to compensate for the small drop in pressure through the vapor line and the coil of the condenser and to produce a slight additional pressure which is sufficient to lift the gasoline to thetop of the tower. For this purpose it has been found that a centrifugal pump is very satisfactory and the latter may very Vreadily vent leakage of the gases hand, where an attempt is be packed in a suitable way to pre- On the other made to supply the refluXing material from storage, considerable difficulty is encountered in the use of the high pressure pumps by way of leakv age around the packing, et

Another advantage derived by the use of' the' present invention is tha other condensatev which is t the gasoline or returned to the tower does not have time to go off' color when it is returned from a point within or immediately beyond the final conde nser. Y Whenever gasoline from storage is relied upon for the refluXing medium, some difiiculty is frequently experienced with the color of the final and product. ,With these other incidental objects and advantages m view, the invention will now be described in detail with reference to the accompanying drawing in which ,p Figure lis a diagramma tic showing of a system illustrating or embodying the present invention and- Figure 2 is a similar view of a modificaN tion.

Referring now to Figure 1, it will be not-ed that there is provided a separating tower or fractionating column 10, which, for the sake 1of illustration, has been shown as of th-e bubble tower type. Vapors may b-e introduced into the tower at a point near the bott-om by means of an inlet pipe 11 which may serve to convey the products of distillation from a still or battery of stills or from any similar source. The vapors so introduced will preferably be under superatmospheric pressure and they will rise within the tower toward the top. In the course of their passage through the tower they will be diverted by suitable means provided in connection with the trays 12. Since the details of the interior construction of the tower do not form a part of the present invention, no further descrip" tion of the same is believed to be necessary. A portion of the vapors in passing through the tower will be condensed and will remain in the trays or will be passed successively to the next lower tray 'by means of suitable overflow vent pipes. Those portions of the vapors which remain in the vapor state on reaching the top of the tower will be conveyed by means of the vapor line 13 into the coil 14 of the iinal con-denser. The latter will preferably be cooled by means of water or other suitable medium which is passed `continuously through the containing vessel surrounding the coil.

At an inter-mediate point, the tubes which go to make up the condenser coil may be eX- Atended through the Icontaining vessel and into a suitable separator. Thus, the mixed vapors and oil may be led through la tube 15 of the condenser coil into the drum of a separator 116. Another tube 17 of the y,coil lleading from the separator will then serve to convey a portion of the mixed vapors `and oil to the balance of the coil `and from the latter into an accumulator drum 18 anda vstorage tank 19. However, another portion of the 'mixed vapors and oil passing through the separator or trap 16 will .be passed through a secondary ou-tlet'20 .and into aseparate coil 21, which may, if desired, be located withi-n the cooling medium in th-e containing vessel of the condenser. In this coil the vapors may be fully condensedand the condensate, which is still under a pressure substantially equal tor that maintained on the tower itself, may be passed through a centrifugal pump 22 and returned by means of the pipe line 23 to the top of the tower. Before entering the tower, the line 23 is preferably divided into two branches which are provided with valves 24 and 25. By proper adjustment of these valves the refluxing medium may be introduced either 'above the uppermost tray or at an intermediate point within the tower, as, for example, onto the fourth tray from the top. It will be apparent that all the centrifugal pump is called upon to do is to compensate for the small drop in pressure through the vapor lin-e 13, the condenser coil 14, trap 16 and coil 21, and in addition, to lift the liquid condensate t-o the top of the tower. This is a comparatively light pressure burden, which the centrifugal pump is readily capable of assuming. The usual packing ditli-culties encountered in the high pressure types of pumps, which give rise to considerable leakage, are thus avoided.

As shown in the drawing, the bottom of the tower 1() may, if desired, be provided with a coil 26 through which the fresh charge of oilv may -be led prior to its introduction into the stil-l which constitutes the source of the vapors arriving through the inlet pipe 11. The coil 26 will thus bring the: fresh charge into heat exchange relation with the 'heated vapors and will tend to cool the latter at the same time that the charge is raised in temperature. This coil may, if desired, be located at the top of the -tower or at an intermediate poi-nt.

In Figure 2 there is illustrated a slight modification of the system disclosed i-n Figure l. As here illustrated, it is possible to locate the separator or trap, which serves to divert a portion of the condensate, at a point between the condensing `coi'l and the accumulator drum, since it vis contemplated that the pressure on the system will be maintained to a point beyond this drum. As shown in this figure, the condenser coil M1 may be of the usual type yand may terminate in an outlet 'pipe 151 leading into the drum 161 of a separa-tor -or trap. A portion of the condensate passing through this trap may'then be led thro-ugh Ian Youtlet pipe 171 into an accumulater dr-um 181v and then into the storage tank 191. Another portion of the condensate may be led through pipe I201 Vinto a centrifugal pump 221 whichmay serve `to return the refluxing material -to the top of the tower. Suitable valves may, as in the system illustrated in Figure 1, serve to control the introduction of the reflux'ing medium -on to the top tray or at an intermediate point.

While the invention has been disclosed in connection with a fractiona-ting column of the bubble tower type, itshould be understood that it lis equally applicable to a fractionating system employing a rock tower or other similar column. Many changes may be made in the form and arrangement of the apparatus employed without departing from the spirit ofthe invention and it is desired to be `limited only by the scope of the claim which follows.

What I claim is:

A process of fractionating vapors of hydrovapors to fractionation under superatmosplieric pressure in a fractionating Zone, cooling vapors from said zone to produce partial condensation, separating the resulting cornbined vapors and condensate into tWo streams, subjecting one stream to further cooling and, prior to any substantial pressure rei duction, returning the resulting condensate to said fractionating zone as a reiluxing medium, and subjecting the other stream to further cooling to produce a final desired distillate.

OTTO BEHIMER. 

